Problem: $-\dfrac{8}{4} - \dfrac{3}{6} = {?}$
Explanation: $ = - {\dfrac{8 \times 3}{4 \times 3}} - {\dfrac{3 \times 2}{6 \times 2}} $ $ = - {\dfrac{24}{12}} - {\dfrac{6}{12}} $ $ = - \dfrac{{24} - {6}}{12} $ $ = -\dfrac{30}{12}$